NC0004626_SPECULATIVE LIMITS_19931012

WDES DOCUMENT SCANNIM& COVER SHEET
NPDES Permit: NC0004626
Document Type: Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Speculative Limits
Staff Report
Instream Assessment (67B)
Environmental Assessment (EA)
Permit
History
Document Date: October 12, 1993
This document i,�printed on reue�e paper--ignore arty
content CUM tUe X-eYeree side
1

State of North Carolina
r Department of Environment,
Health and Natural Resources ` •
Division of Environmental Management
James B. Hint, Governor C F1
Jonathan B, Howes, SecretaryC
A. Preston Howard, Jr,, P.E., Director
October 12, 1993
J.W. Buchanan
PPG Industries
P.O. Box 949
Lexington, NC 27293
Subject: PPG Industries Speculative; Limits
NPDES No. NC0004626
Davidson County
4
Dear Mr. Buchanan:
The Division of Environmental Management (DEM) has reviewed your request for
speculative NPDES Permit limits for the PPG Industries. The Division is initiating a basinwide
water quality management strategy for the state's surface waters. All NPDES permits within a
given basin will be renewed in the same year, allowing the Division to examine interaction among
all point and non-point sources of pollutants for that basin. The basin plan for the Yadkin Basin
will be promulgated by 1998 and a draft version will be available for public comment sometime in
1997. In the meantime, discharge limits will be based on existing procedures. In addition, my
staff is currently developing a nutrient response model of High Rock Lake. Tile outcome of this
model will affect future permits for discharges to High Rock Lake.
The lake arms of High Rock Lake do not assimilate wastewater well. Grants Creek, Town
Creek, and Abbotts Creek have all experienced serious water quality impairment due to point
source discharges. The City of Salisbury plans to relocate its WWTPs to the Yadkin River and
build a new state-of-the-art WWTP while the Abbotts Creek WWTPs must continue to provide
state-of-the art treatment in order to minimize water quality violations- Though the summer 7QIO
in Swearing Creek is nearly ten times greater than that in Potts Creek, the assimilative capacity at
the proposed discharge site oil Swearing Creek is limited. The assimilative capacity for oxygen-
consuming wastes is driven by the slope of the streamhed in addition to dilution provided by the
streamflow. Since this stream flows into a lake there is little or no change in slope as the stream
approaches the lake boundary.
Swearing Creek received effluent from the City of Lexington until 1986. -The Lexington
WWTP had permit limits of BOD5 = 12 nag/1 and NH3 = 4 mg/l, an ultimate BOD of 54 mg/l,
and no nutrient limits. Biological sampling upstream and downstream of the plant showed the
RO. Box 29535,Raleigh, North Carolina 27626-0535 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 6C%recycled/ 1 Q%post-consumer paper

Y i
WWTP to have negative impacts on the stream. Localized algal blooms occurred and there were
DO violations. Ultimately the WWTP was removed and monitoring data show Swearing Creek
has recovered.
PPG currently has a permitted ultimate BOD of 114 mg/1 based on federal guidelines. If
you choose to relocate the PPG discharge to Swearing Creek, more stringent BOD limits and
state-of-the-art nutrient limitations will be required. A plant with a high degree of flexibility to
include nutrient removal should be considered. The fecal coliform limits will be 200
colonies/100 ml. In addition, dechlorination or alternate disinfection will be required.
The above limits are speculative and are for use in an engineering review of discharge
alternatives. Final limits will be provided upon receipt of an application for permit expansion. If
you have any questions concerning the above issues, please call Betsy Johnson at [phone].
Sincerely,
Ruth Swanek
Water Quality Section
RCS/eaj
cc: Winston-Salem Regional Office
Central Files